Surface coating compositions comprising plaster of paris and method of producing the same



June 14, 1966 G. B. HEIJMER 3,256,223

SURFACE COATING COMPOSITIONS COMPRISING PLASTER OF PARIS AND METHOD OF PRODUCING THE SAME Filed July 12, 1962 INVENTOR ATTORNEY United States Patent 12 Claims: Cl. 260-22) This invention relates to surfacing or coating compositions, particularly of the type adapted for use as so-called spackling compounds, and to methods of producing and packaging the same.

Conventional spackling compounds are composed principally of mixtures of different granular or pulverized minerals, such as sand, and a binder consisting of an aqueous solution of an organic adhesive such as a watersoluble cellulose derivative. These compositions are conventionally packaged for storage and shipment in the form of a moist, fairly coarse product. The product may be removed, as by means of a shovel, scoop or similar tool, directly from the containers in which it is packaged and shipped.

By reason of the fact that these compositions are of a nature such that they cannot be exposed to the open air for any substantial period of time without suffering damage from drying, they must be stored and transported in containers which are impervious to water and water vapor. Accordingly, the product is shipped to large users in tin containers of five to ten gallon size. In the case of shipment for re-sale to customers desiring to use the product for small repair jobs, it is generally packaged and shipped in polyethylene bags of one to two quart size.

Since the cost of production of the surfacing material itself is relatively low, the cost of packaging the same inordinately increases the price of the product to the ultimate consumer. Furthermore, the large size containers or drums are unwieldy to handle and, after emptying, cause considerable annoyance and expense in. removing the same from the place of use, since they cannot be reused for packaging of new material.

The principal object of the present invention is to provide a coating or surfacing composition of the type described, which will in many respects be superior to the heretofore known compositions of this general type,

Another object of the invention is to provide a coating or surfacing composition of the character set forth and which may be packaged for storage and shipment in plastic containers.

Stated briefly, the coating or surfacing composition of the present invention, in contrast to the known compositions, contains among its ingredients, plaster of Paris and water in such proportions that the product will, in less time than half an hour after the ingredients have been properly mixed together, harden into a coherent, solid body characterized by its ability to be transformed, when desired, and through simple mechanical means, into a loose mass of plastic consistency equal or superior to that which characterizes the conventional surfacing or coating compositions composed of sand and an organic binder.

It is a feature of the'invention that the composition hereof, after being transformed from the above-mentioned condition as a coherent, solid body, into the form of a spreadable mass, does not harden against into a coherent solid body unless and until the water content thereof has been eliminated.

By reason of the afore-mentioned transformation of the coherent, solid body into a loose, spreadable, mass, the latter possesses an extraordinary fine plastic consistency resembling that of butter at room temperature, provided the content of Water and plaster of Paris in the mass is restricted within certain limits as hereinafter set forth; The product is homogeneous and easily spreadable, and'its extraordinary malleability and plasticity enable it to be spread in thinner and smoother layers than has been possible with the heretofore known compositions. It is thus particularly suitable for surfacing work. Furthermore, if desired, the composition may be applied in layers of considerable thickness, say up to as much as one centimeter, without shrinkage or collapse of the composition. Thus,it is possible to apply the composition in a layer of desired thickness over an old coating layer without forming a visible joint or juncture line between the old and the new coating layers, whether the new coating layer is of the same or a different thickness than that of the old coating.

In accordance with the invention, the composition hereof may readily be packaged for storage and shipment in the form of a coherent solid body contained in a plastic bag or container which is impermeable to water and water vapor and which may readily be stripped away at the place and time of use of the product. When thus removed or otherwise separated from the container, the composition may readily be transformed into a loose mass of readily spreadable consistency by simple comminuting action such as by rubbing the same under slight pressure against a rough surface or by mechanism such as hereinafter referred to.

Since, as above stated, the composition hereof, after being transformed from the solid, coherent condition into a spreadable mass, does not revert to a solid mass unless its water content iseliminated, it becomes possible in accordance with another embodiment of the invention to prepare the same in the form of a product suitable for direct use as a surfacing or coating material. The product in that form may be packaged for storage and shipment in a plastic or other suitable container impermeable to water and water vapor. According to this embodiment of the invention, the mass may be prepared directly in the form of a spreadable product by intensive mixing and mechanical working of the ingredients.

Further, in accordance with the invention, the plasticity and malleability of the composition hereof may be greatly enhanced by incorporating therein bentonite and/or aqueous emulsions of water-insoluble binders like polyvinyl acetate and acrylic resin emulsions. Particularly suitable for this purpose are emulsions of either the water-in-oil or the oil-in-water type which contain alkyd resins modified with, say, of a suitable fatty acid or with a condensation product obtained by condensing two parts by weight of phthalic acid with one part by weight of glycerol and two parts by weight of castor oil. It has further been found that coating or surfacing layers made of compositions which contain these emulsions acquire a considerably enhanced mechanical strength.

With regard to the use of bentonite and/or emulsions in producing the compositions hereof, it has been found preferable to first mixthe plaster of Paris with these materials and thereafter add the other ingredients to the thus-obtained mixture. The bentonite may suitably be added in its dry form at the same time as the other ingredients of the mixture are added. The bentonite, however, may be added in the form of an aqueous suspension which is mixed into the binder emulsion.

Stated in general terms, the compositions according to the present invention contain plaster of Paris in the range of between and 45% by weight, calculated as calcined plaster of Paris. The water content of the compositions may range between and 60% by weight of the total weight of the compositions, the percent of water content being figured as including the amount which becomes bound with the calcined plaster of Paris during the hard ening of the mass.

With regard to the inorganic filler portion of the composition, this may include graded sand, limestone, pumice stone, chalk ground marble, and the like. Preferably, these are of grain sizes graded for example, as described in U.S. Patent 2,700,615 or U.S. Patent 3,002,853.

In producing the composition of the invention, the ingredients thereof may be combined in a single step operation wherein the various ingredients are added in a certain predetermined order in a suitable mixing device in which they are worked into one another. Alternatively, water and plaster of Paris in predetermined proportions may be added to a pre-mix of the other ingredients. This pre-rnix may be one freshly made or one which has been stored for a period of time. This alternative method of combining the ingredients of the composition has the advantage that manufacturers of the known type of coating or surfacing compositions may readily utilize the latter to produce the compositions of the present invention therefrom by merely adding and carefully mixing into a certain amount of the conventional composition, whether the latter is fresh prepared or has been in storage, a freshly prepared pre-mix of plaster of Paris and water. This pre-mix of plaster of Paris and Water may consist, for example, of equal proportions by weight of calcined plaster of Paris and water, together with a small amount of a so-called retarder which makes it possible to adjust the setting-time, such as powdered animal adhesive, dextrine, sugar, borax, or other substances known to possess the property of retarding the water absorption and hardening or binding of plaster of Paris.

The addition of as small an amount as 5% by weight of the above-mentioned pre-mix of plaster of Paris and water to surfacing compositions of the conventional type will result in a product which may be packaged for shipment in suitable soft containers in which it will harden into a coherent, solid body capable of being stored and shipped without requiring the use of cumbersome and wasteful stiff containers of wood or tin.

In order to impart the proper plasticity to the spreadable composition resulting from the light mechanical action upon the solid body, it is generally necessary that substantially more than 5%, preferably in the range of 10 to 50%, by weight, of the aforesaid pre-mix of plaster of Paris and water be added to the conventional composition. Products having practical application have been obtained with pre-mixes of equal parts by weight of plaster of Paris and water, added in amounts as high as 200% by weight, based on the total weight of the other ingredients of the conventional surfacing compositions.

In the compositions containing aqueous emulsions of water-insoluble binders as referred to above, the amount of plaster of Paris added may be between 10 and and the amount of water added may be between 25 and in each instance by weight, based on the total weight of the composition. The stated percentages are inclusive of the water present in the binder emulsion, but exclude the water which remains absorbed in the air-dry raw materials and water of crystallization in the calcined plasterof Paris.

The following examples represent specific illustrations of mixtures which have been found capable of forming the solid coherent bodies according to the invention.

Example 1 Kg. Stored coating 96\ Plaster of Paris in the form of mush 4 Total 100 The stored coating is one made according to U.S. Patent No. 2,700,615 and may have the following compositions:

Percent by weight Methyl cellulose 1.3 Graded sand 50.0 Ground chalk 24.0 Pumice stone 2.7 Plaster of Paris 2.0 Water 20.0

Total 100.0

The plaster of Paris mush may have the following compositions:

Percent by weight Plaster of Paris (stucco) 48 Water v 48 Bentonite 2 Hydrolysed animal adhesive 2 Total 100 Examples 2 to 6 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6

Percent by weight Plaster of Paris (Stucco) 2 10.0 30.0 40. 0 5.0 Graded sand 55 65. 0 32. 0 18.0 70. 0 Water 20 20. 0 35. 0 40. 0 1s. 0 Water soluble cellulose derivative 1 3. 2 0. 3 1. 0 2. 5 Bentouite 0.3 1.0 0.5 halk Emulsion of synthetic resins l. 5 2v 7 4. 0

In those cases where the composition is to be packaged for storage and shipment in the form of a coherent solid body, the mixture of the ingredients is intimately worked until it acquires a thick mushy consistency. It is then poured into bags or cylindrical containers of suitable plastic or like material, such as polyethylene, impervious to Water and water vapor. Within a relatively short time, of the order of about one-half hour, the composition hardens into the form of a coherent, solid body within the container, and is ready for storage and shipment thereof. Desirably, after the mixture has been poured into the containers, the latter and their contents are permitted to remain undisturbed until the mass in the container has hardened into a fairly ,solid body. Where the containers employed are bags or casings made of polyethylene, polystyrene or other pliable plastic material, the containers are desirably held within relatively stiff supporting cylinders on a fixed support so that the pliable containers and their contents will remain undisturbed in the cylinders until the mass in the containers has hardened into a solid body for storage and shipment.

At the place of use, the solid body may be separated from its containers, as by stripping away the latter, and then crushed and mechanically worked so that it is reconverted into a loose, granular mass of spreadable plastic consistency, which it will retain as long as the mass. retains its moisture content.

. tions to the rear thereof.

In those cases where the composition is to be packaged for storage and shipment in directly useable form, the ingredients are intensively mixed and mechanically worked until the mass assumes a loose, granular, plastic condition. In that condition, the composition may be packaged for storage and shipment in containers of polyethylene or like pliable plastic material which is not penetrable by water or water vapor.

In order to reconvert the composition hereof from its solid body form into the loose, granular form in which it is of plastic, spreadable consistency, a rubbing action of the same under relatively light mechanical pressure against a rough surface may be employed, the nature of the solid body being such that it acts somewhat analagously to ordinary writing chalk or pencil lead. However, this expedient may not be fully eifective in commercial practice.

Accordingly, for that purpose, use may be made of the mechanical arrangement depicted in the accompanying drawing.

As shown in the single figure of the drawing, this arrangement comprises a relatively elongated cylindrical chamber into which the composition in solid-body form may be delivered through an upwardly extending hopper 11. At its forward end, the chamber is formed with a frusto-conical section 12, joined at its outer smaller end to a reverse frusto-conical section 13. The latter is connected to a frusto-conical end section 14 having an opening 15 at its lower side, leading to a discharge tube 16.

Extending axially through chamber '10 and sections 12-14, is a rotatable shaft 17, driven as by suitably arranged gears and chains 18, from a motor indicated at 19.

Mounted on shaft 17 is a spiral vane 20 extending from the rear end of the chamber to the forward end of section 12. As will be noted from the drawing, that forward portion 21 of the vane 20 which operates within section 12 is of smaller diameter than that of the por- The diameters of portion 21 and of the flight immediately to the rear thereof are somewhat less than that of the interior of the respective sections or portions of the chamber in which they are disposed.

Mounted on the portion of shaft 17 within section 13 of the working chamber is a frusto-conical cylinder 22, dimensioned radially so as to provide an annular pas sageway 23 of gradually decreasing radial dimension between the interior surface of section 13 and the surface of the cylinder. The latter is preferably grooved or corrugated lengthwise thereof.

As will be evident, the solid-body material delivered to the chamber will be propelled forwardly by the rapidly rotating spiral or screw conveyor 20 into the working section of the chamber and forced by the pressure of the conveyor through passageway 23. As a result, the material will be crushed and transformed into the form of a loose, granular mass of plastic, spreadable consistency by the time it reaches section 14 and is discharged from the chamber through section 14 and outlet 16. If desired, a spiral vane 25 may be mounted on shaft 17 in the discharge section 14, to assist in discharging the material.

Although the apparatus illustrated in the drawing and described above has been found suitable in actual practice of the invention, it should be evident that other suitable means may be employed for converting the composition hereof from its solid-body condition into the form of a loose, granular mass. Other such means may take the form of a power press, viz, the solid bodies may be crushed in the cylinder of a hydraulically driven piston press and by pressing out the mass through openings in a counter-pressure disk disposed at the discharge end of the cylinder, the disk being provided with openings of about one millimeter size. The counter-pressure disk may be composed of a large number of corrugated plate members having a width of a few centimeters and a thickness not in excess of one millimeter, these plate members being-assembled in positions such that the ridges of the corrugations on adjacent members engage one another, tangentially, whereby to form a series of parallel channels or canals of the same length as the width of the members and extending in the direction in which the piston pressure is applied. Alternatively, the counterpressure disk may be composed of a corrugated plate member, with the corrugations formed in such a manner that it looks like a so-called cross-corrugation.

What is claimed is:

1. A packaged product for forming surfacings or coatings, comprising a composition consisting essentially of:

(a) graded sand,

(b) graded mineral filler of particle sizes, smaller than those of said graded sand,

(c) a water-soluble organic adhesive binder,

(d) plaster of Paris in the range of about 10% to about 45% by weight based on the total weight of the composition, and

(e) water said water being present in an amount within the range of about 25% to about 60% based on the total weight of the composition, said amount of water serving to cause the composition to harden into a coherent solid body within about one half hour after complete mixing of said ingredients, said hardened body being readily comminutable by simple mechanical action into the form of a spreadable, loose, granular mass of plastic consistency which does not reharden into a coherent solid body until the water content of said spreadable mass is eliminated.

2. A packaged product defined in claim 1, wherein the largest granules of said graded sand do not exceed 0.8 mm. in size, and the smallest granules thereof are not less than 0.3 mm. in size.

3. A packaged product defined in claim 1 wherein said mineral filler is selected from the group consisting of ground chalk, limestone, pumice stone and mixtures thereof.

4. A packaged product as defined in claim 1, and containing 'bentonite in an amount in the range of about 0.08% to 1.0 by weight of said composition.

5. A packaged product as defined in claim 1, and containing an aqueous emulsion of water-insoluble organic binding material capable of imparting enhanced mechanical strength to the coating or surfacing layers formed from said composition.

6. A packaged product as defined in claim 5, wherein said organic binding material is a modified alkyd resin.

7. A process of preparing a coating or surfacing composition, said method comprising (a) preparing a mixture consisting essentially of:

( 1) graded sand;

(2) graded mineral filler of sizes smaller than those of said graded sand;

(3) a water-soluble organic adhesive binder; and

(4) water,

(b) incorporating into the aforesaid mixture a pre-mix consisting of:

(1) plaster of Paris; and

(2) water, said pre-mix (b) being utilized in an amount within the range of 4% to 200% of said mixture (a), to provide a composition containing water in an amount within the range of about 25% to about 60%, and plaster of Paris in an amount within the range of about 10% and about 45%, each based on the total weight of the composition,

(c) intimately stirring the whole mass until it acquires a mush-like consistency,

(d) pouring the resultant mush-like mass into plastic containers impermeable to water and water vapor, and

(e) permitting said mass to harden into a coherent solid body in said containers.

8. A process as defined in claim 7, wherein said pre-mix (b) contains plaster of Paris and water in approximately a 1:1 ratio.

9. A process as defined in claim 7, wherein said pre-mix (b) is utilized in an amount approximately 50% by weight of said first-named mixture (a).

10. A process as defined in claim 7, wherein said pre-mix (b) contains a substance serving to retard the binding elfect of the plaster of Paris.

11. A process of preparing a coating or surfacing composition, said method comprising (a) preparing a mixture consisting essentially of:

(1) graded sand; (2) graded mineral filler of sizes smaller than those of said graded sand; (3) a Water-insoluble organic adhesive binder; (4) plaster of Paris; and (5) water, the amount of said plaster of Paris being in the range of about to about 45% by Weight of said mixture, and the amount of water being in the range of about 25% to about 60% by Weight of said mixture,

(b) intimately stirring said mixture until it acquires a mush-like consistency; v

(c) pouring the resultant mush-like mixture into plastic containers impervious to water and Water vapor, and

(d) permitting said mixture to harden into a coherent solid body in said containers.

12. A process of preparing a coating or surfacing composition, said method comprising 8 (a) preparing a mixture consisting essentially of:

(1) graded sand; (2) graded mineral filler of sizes smaller than those of said graded sand;

(3) a water-insoluble organic adhesive binder;

(4) plaster of Paris; and

(5) water, the amount of said plaster of Paris being inthe range of about 10% to about by weight of said mixture, and the amount of water being in the range of about 25% to about by weight of said mixture,

(b) intensely working the mixture to convert the same into a loose, granular mass of plastic consistency, and

(c) pouring said mass into flexible plastic containers impermeable to water and water vapor.

References Cited by the Examiner UNITED STATES PATENTS 632,482 9/1899 Van der Vijgh et a1. 106-111 1,871,806 8/1932 Roos 106-111 2,371,688 3/1945 Gold 106-111 2,700,615 1/ 1955 Heijmer 106-93 3,002,853 10/1961 Heijmer 106-171 3,054,687 9/1962 Montgomery et a1. 106-111 3,069,278 12/1962 Kimpel 106-110 LEON J. BERCOVITZ, Primary Examiner. DONALD E. CZAIA, Examiner.

R. W. GRIFFIN, Assistant Examiner. 

1. A PACKAGED PRODUCT FOR FORMING SURFACINGS OF COATINGS, COMPRISING A COMPOSITION CONSISTING ESSENTIALLY OF: (A) GRADED SAND, (B) GRADED MINERAL FILLER OF PARTICLE SIZES, SMALLER THAN THOSE OF SAID GRADED SAND, (C) A WATER-SOLUBLE ORGANIC ADHESIVE BINDER, (D) PLASTER OF PARIS IN THE RANGE OF ABOUT 10% TO ABOUT 45% BY WEIGHT BASED ON THE TOTAL WEIGHT OF THE COMPOSITION, AND (E) WATER SAID WATER BEING PRESENT IN AN AMOUNT WITHIN THE RANGE OF ABOUT 25% TO ABOUT 60% BASED ON THE TOTAL WEIGHT OF THE COMPOSITION, SAID AMOUNT OF WATER SERVING TO CAUSE THE COMPOSITION TO HARDEN INTO A COHERENT SOLID BODY WITHIN ABOUT ONE HALF HOUR AFTER COMPLETE MIXING OF SAID INGREDIENTS, SAID HARDENED BODY BEING RADILY COMMINUTABLE BY SIMPLE MECHANICAL ACTION INTO THE FORM OF A SPREADABLE, LOOSE, GRANULAR MASS OF PLASTIC CONSISTENCY WHICH DOES NOT REHARDEN INTO A COHERENT SOLID BODY UNTIL THE WATER CONTENT OF SAID SPREADABLE MASS IS ELIMINATED. 